Speaking after an emergency meeting of top security officials, Cazeneuve said all elite units were on top alert for the election to back up the 50,000 police already earmarked for special election duty.

"The government is fully mobilised. Nothing must be allowed to impede the fundamental democratic process of our country. It falls to us not to give in to fear and intimidation and manipulation which would play into the hands of the enemy," he said in a statement.

The first round in France's two-stage election will be held on Sunday with a second final round on May 7.